FWIW, you will soon be able to get that effect without a metafunction. from http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#106 [example] int i; typedef int& RI; RI& r = i; // r has the type int& const RI& r = i; // r has the type const int& [/example]
I'm not sure I like it, because a 'RI const' is 'int&', but a reference to a 'RI const' is 'int const&'. But maybe its useful that way.
Oh, that's very disturbing. What is the rationale for moving the const inside the reference?
Ah, I see it in N1245:
template<class T> class X { f(const T&) ; /* ... */ };
X<int&> x; // X<int&>::f has the argument type const int&
I'm not convinced that special rule is worth the breath and text needed to explain it. With any well-behaved class X, if f was written to work on a "const X&" argument, it will work equally well and correctly on a "X&" argument.
It's probably too late for objections now, though.
I don't think this affects add_const as such: Adding a const qualifier to a reference type still has no effect, it's only when you add a reference qualifier to a reference type that the cv-qualifiers get combined in this way. Assuming I've understood correctly of course! John.